The present invention generally relates to water treatment systems, and more particularly to the operation and cleaning of a water treatment system designed to remove metal ions from water.
Industrial, mining, agricultural, and various natural processes often produce considerable amounts of waste water. This water is frequently contaminated with a variety of undesirable materials ranging from organic solvents to metal ions. The removal of metal ions from water is of particular importance, especially with respect to heavy metal ions (e.g. Ni.sup.+2, Cu.sup.+, Co.sup.+2, Zn.sup.+2, and the like). These metals may present considerable environmental and toxicity problems. Thus, it is important that they be removed from waste water in an efficient manner and disposed of properly.
Many chemical and physical techniques have been developed for removing metal ions from water. However, one recently-developed, highly efficient technique involves the use of polymer materials (preferably in the form of beads or other small units) having metal ion extracting agents therein. These materials are described in copending U.S. patent application Ser. No. 429,236 filed on Oct. 18, 1989 (incorporated herein by reference). This application specifically involves polymeric beads made of polysulfone, cellulose acetate, or other polymers having various metal ion extracting agents therein. Exemplary metal ion extracting agents include but are not limited to selected biomass materials (e.g. yeast, algae, molds, xanthan gum, guar gum, alginates, and mixtures thereof). Other extracting agents include but are not limited to triisooctyl amine, di-2-ethylhexyl phosphoric acid, tri-octyl methylammonium chloride, 2-hydroxy-5-dodecylbenzophenone oxime, and di-2-4,4-trimethylpentyl phosphinic acid.
Exemplary bead materials are prepared by first dissolving high-density polysulfone in an organic solvent known in the art (e.g. dimethylformamide [DMF]). Next, the desired biomass or chemical extractants are mixed with the polysulfone-DMF mixture. To facilitate this procedure, the biomass/extractants may first be adsorbed onto activated carbon.
After this step, inert metal powders (e.g. magnetite) may be combined with the mixture to increase bead density and/or impart magnetic properties to the beads. Finally, the mixture is injected through a nozzle into water, whereby spherical beads preferably ranging in size from about 1/64 to 1/4 inches in diameter are immediately produced. The beads have a relatively intricate internal pore structure, with the biomass/extractants being immobilized therein. It is preferred that the beads be fabricated from mixtures containing about 75-200 g of polysulfone per liter of solvent. It is also preferred that polar solvents be used to produce the beads, and other representative solvents which may be used include dimethyl sulfoxide, tetrahydrofuran, acetone, and mixtures thereof. Other biomass materials of interest include penicillium mold and common duckweed (Lemna sp.).
The polymeric units (e.g. beads) described herein are highly efficient in removing metal ions from waste water. Specifically, metal ions in the waste water flow into the internal pore structures of the polymeric units where they are retained therein by the biomass/extractants. However, in order to efficiently use the units for large scale water treatment purposes, they must be periodically "regenerated". Regeneration (e.g. cleaning) involves the removal of metal ions from the units so that they may be reused. The present invention specifically provides a method for water treatment in which a rapid and efficient procedure is disclosed for regenerating the polymeric units. This method greatly facilitates the entire water treatment process and represents an advance in the art of water purification technology, as described in detail herein.